Sources & references
Our conversions aren’t copied from a chart — they’re computed from published standards and cross-checked. Here’s what we rely on.
Last reviewed: June 24, 2026
- ISO 8653:2016 — Jewellery, ring sizes
- The international standard defining ring sizes by inner circumference in millimetres (the basis of EU/ISO sizing).
- JIS S 4700 — Japanese ring sizing
- The Japanese Industrial Standard for the JP ring-size scale.
- Ring size — Wikipedia
- Reference for the governing US diameter/circumference formulas and a cross-check of national systems.
- US jeweler diameter standard
- The de-facto US scale: size 0 = 0.458 in inner diameter, +0.032 in per whole size — the engine behind our table.
- European / ISO 8653 reference (ringsizes.biz)
- Confirms EU/ISO circumference basis and EN 28653 adoption.
See exactly how we use these in how we calculate ring sizes, then check a value in the converter or the full chart.